1. Field of the Invention
The present invention relates to apparatus and methods for performing minimally invasive surgery. More particularly, the invention relates to a method of accessing the mediastinum and the pericardium using a single subxiphoid incision, and using an endoscopic cannula to access all regions of the heart.
2. Description of the Related Art
Several different incisions have traditionally been used to access mediastinal organs, such as the heart (surrounded by the pericardium), the esophagus, and lymphatic glands. Examples of such incisions are sternotomy (a division of the patient's sternum) thoracotomy (an incision between two adjacent ribs) and a subxiphoid incision to create a pericardial window by exposing and excising a portion of the pericardium. For example, a subxiphoid incision has been made to allow excision of the xiphoid, and retraction of the sternum upward to expose the anterior pericardium.
These procedures, however, are all quite invasive, requiring large incisions or open heart surgery. Thoracotomy is additionally invasive as it requires the deflation of one or both lungs, since the approach is via the pleural cavity. Nevertheless, when it is desirable to access other regions of the heart than merely its anterior region, the current practice is to employ these invasive methods to dislodge the heart from its resting place within the pericardium, so that all regions of the heart may be accessed and cardiac procedures performed. For example, to access both left and right sides of the heart, as well as the posterior and anterior regions, surgeons are currently using a partial or full sternotomy (i.e. a partial or full division of the patient's sternum) to gain access to the several regions of the heart by permitting the heart to be rotated or lifted out of its resting place in the chest. Such a procedure, however, is too invasive, and thus not desirable.
With the advent of minimally invasive surgery, approaches have been developed using smaller access incisions or ports. Coronary bypass surgery has been performed on the beating heart through direct incisions in the chest and abdomen, including sternotomies and thoracotomies. A subxiphoid incision has been used to anastomose a gastroepiploic artery to the posterior descending coronary artery for coronary artery bypass. These procedures, however, have been performed under direct vision, and thus still require a fairly large incision to assist the surgeon in observing the field of surgery.
To achieve even less invasive surgery, it is desirable to perform cardiac procedures endoscopically. Endoscopic coronary bypass surgery has been performed on a stopped heart following the institution of cardiopulmonary bypass. In this procedure, ports are placed in the intercostal spaces, through the chest wall, to allow placement of the endoscope and operating instruments. This method, however, does not enable the surgeon to access all regions of the heart. With port access surgery or beating heart surgery from a limited thoracotomy, only one side of the heart is accessible. For example, with a left thoracotomy or the introduction of left side ports, surgery is limited only to the left side of the heart. Endoscopic harvesting of the gastroepiploic artery for coronary artery bypass surgery has also been described, involving standard laparoscopic techniques of gas insufflation and introduction of laparoscopic forceps, scissors, and staplers. However, none of these minimally invasive methods allow access to all regions of the heart. Thus, a method and apparatus are needed to allow safe and minimally invasive access to all regions of the heart for performing cardiac procedures.
In addition, conventional procedures such as open heart surgery, port-access surgery using trocar ports and an endoscope, or beating heart surgery through a partial sternotomy or thoracotomy, all require making a large incision in the pericardium to expose the heart. In the prior art, methods of accessing the heart to perform cardiac procedures involved making an incision in the pericardium using a sharp-edged instrument through an incision in the chest. As the heart typically underlies the pericardium contiguously, the surgeon is presented with the difficult task of incising the pericardium without accidentally cutting the heart. To avoid this difficulty during port-access surgery, a second incision into the skin is also required to allow the insertion of forceps to pull the pericardium away from the heart. This allows the incision of the pericardium to be executed more safely. However, this technique requires multiple incisions in the patient and requires the advancement of multiple instruments in separate passageways to the pericardium.
In addition to requiring several incisions, the conventional techniques also typically require the incision in the pericardium to be lengthy. The sharp-edged instrument must slice a cut of sufficient length to allow the insertion of other surgical tools into the pericardium. At the end of the cardiac procedure, it is desirable to close the pericardial incision if possible, to reduce fibrous adhesions to the heart and pericarditis. With endoscopic port-access surgery, a long pericardial incision is difficult to close, due to the complexity of endoscopic suturing.
Another problem arising in conventional cardiac procedures is the dissection of a working tunnel from the initial incision to the pericardium. Mechanical probing of heart tissue may cause severe or dangerous cardiac arrhythmias such as ventricular fibrillation. Therefore, it is desirable to use a small dilating instrument to create the initial tunnel. However, the instruments currently available to perform cardiac procedures are typically large, and therefore a larger cavity must be dissected to allow these instruments to pass through to the pericardium. Although using a larger dilator may create the necessary space, a larger dilator may cause damage to the heart by causing cardiac arrhythmias as discussed above. If a smaller dilator is used to minimize this potential trauma, the working cavity may not be large enough to allow the larger instruments required in the procedure to be advanced to the pericardium. A further problem with conventional dilators such as balloon dissectors is that such tools exert shear force on the surrounding tissue as they are advanced in the body. Shear force has a tendency of causing vessel avulsion and tissue abrasion.
Various other schemes and devices have been previously devised in an attempt to enter the pericardium via a small portal of entry, or via a percutaneous puncture site. None of these systems permit reliable, safe entry under direct, endoscopic visualization. U.S. Pat. No. 5,931,810 (Grabek) describes a grasping instrument with jaws that grasp the pericardium followed by advancement of a needle through a bore in the shaft of the instrument. The needle extends between the closed jaws of the device, into the pericardium. This concept suffers from unreliability, as it is difficult to ensure that the needle will pierce between two layers of pericardium that are compressed by the jaws of the device, without an active technique of holding the two opposed layers of pericardium apart. Thus, as there is no central cavity in a flap of pericardium grasped by the instrument jaws, a needle advanced down a central bore of the instrument may easily end up outside of the pericardium, or embedded in the pericardium, instead of lying between the two layers of pericardium pinched together by the jaws. Also, axial advancement of the needle carries the potential of myocardial puncture. Needle entry with the Grabek device must be verified by subsequent passage of a guidewire into the pericardial sac, or by infusion of fluid or contrast material through the needle into the pericardial cavity.
U.S. Pat. No. 5,827,216 (Igo et al.) and U.S. Pat. No. 5,972,013 (Schmidt) both describe tubes that are placed in contact with the pericardium, applying a vacuum to pull a bleb of tissue into the tube, followed by penetration of the pericardial bleb with a needle. These techniques are unreliable, because there is generally a layer of fatty tissue adherent to the pericardial surface, and suction may pull fat into the tube instead of pericardium.
U.S. Pat. No. 5,071,428 (Chin et al.) describes a clamp with distal points that grasp a flap of pericardium, allowing a guidewire to be advanced within tubular guides to puncture through the pericardium. A tube may follow the guidewire into the intra pericardial space. This design may cause myocardial trauma due to the sharp pointed grasping clamp. The multiple steps of pericardial grasping, pericardial puncture, guidewire advancement, and catheter insertion render this technique impractical.
Therefore, apparatus and methods are needed to provide safe and minimally invasive access to all regions of the heart during cardiac procedures, requiring a minimum number of incisions, and without requiring a long incision either for initial access or at the pericardium. The proposed technique of this application allows reliable and safe entry into the pericardium under continuous endoscopic visualization.